1. Field of the Invention
The present invention relates to the synthesis of azines and more especially, to the production of hydrazine.
2. Description of the Prior Art
Hydrazine, typically in the form of hydrazine hydrate, is a widely used compound, whether as such or as a synthesis intermediate. According to Ullmann, 5th edition, vol. A 13, pages 177-191 (1989), hydrazine is produced either by the oxidation of ammonia with chlorine or a hypochlorite bleach solution, optionally via a ketazine, or by reacting aqueous hydrogen peroxide with ammonia and a ketone.
The aqueous hydrogen peroxide process is well known to this art and has been described, for example in U.S. Pat. Nos. 3,972,878, 3,972,876, 3,869,541, 3,948,901, 3,919,256, 3,943,152 and 4,093,656.
In this process, ammonia, aqueous hydrogen peroxide and a compound bearing a&gt;C.dbd.O group, such as a ketone, are interreacted according to the following reaction scheme: ##STR1##
The reaction is carried out in the presence of catalyst.
The azine can then be hydrolyzed into hydrazine hydrate according to the mechanism: ##STR2## with the ketone being regenerated.
U.S. Pat. No. 3,972,878 describes such reaction in the presence of a mixture of an amide of a weak acid and of a phosphate. Such mixtures include, for example, acetamide with lithium phosphate, acetamide with sodium carbonate, propionamide with lithium phosphate, acetamide with disodium phosphate and acetamide with diisopropyl phosphate.
The azine yield based on the aqueous hydrogen peroxide ranges from 45% to 55% and increases to 78% when using the acetamide/disodium phosphate pair.
U.S. Pat. No. 4,093,656 also describes, in a reaction for the synthesis of azines, a catalyst which is a mixture of three compounds, namely, an amide of a weak acid, the ammonium salt corresponding to this acid and another compound such as a phosphate. Such mixtures include, for example, admixture of acetamide, ammonium acetate and sodium phosphate. The azine yield based on the aqueous hydrogen peroxide is as high as 85%.